In the novel, Lord of the Flies, what is Ralph uneasy about in the beginning? Who comforts him and what does he say?

Ralph, is in fact, mostly unconcerned. He relishes the idea about being on an island as illustrated by the following quotes:

Ralph danced out into the hot air of the beach and then returned as a fighter-plane, with wings swept back, and machine-gunned Piggy.

Ralph did a surface dive and swam under water with his eyes open; the sandy edge of the pool loomed up like a hillside. He turned over, holding his nose, and a golden light danced and shattered just over his face.

Here was a coral island. Protected from the sun,
ignoring Piggy’s ill-omened talk, he dreamed pleasantly.

Here at last was the imagined but never fully realized place leaping into real life. Ralph’s lips parted in a delighted smile and Piggy, taking this smile to himself as a mark of recognition, laughed with pleasure.

It is obvious that being here is nirvana for Ralph. In fact, when we are introduced to him, he clearly relishes being on the island and displays no concern whatsoever. He undresses and goes for a swim, throws sand on his body and enjoys the warmth of the sun.

Piggy, the other boy, is the one who expresses his unease in a variety of ways. He firstly speaks about there being no adults around to supervise them. He then expresses the notion that all the others who were on the plane with them could have died in the crash. He furthermore voices concern about the fact that they might be on an island and that they might not be rescued. Ralph concedes that it might be an island and assures Piggy that they would be rescued:

“I could swim when I was five. Daddy taught me. He’s a commander in the Navy. When he gets leave he’ll come and rescue us.

Piggy wants to know when this will happen and Ralph tells him that he would do so as 'soon as he can.' Ralph is quite unperturbed about their situation. Their rescue is of no immediate worry to him. It is Piggy who is anxious and finicky, especially about his health, his 'ass-mar', which Ralph dismisses with disdain by saying, 'Sucks to your ass-mar!'

Piggy consistently refers to their being on an island since he realises that, if it were so, the chance for rescue would diminish dramatically. Ralph, on the other hand, does not much care.